The enlarged intertrochanteric region at the upper end of the human thigh bone (in latin “femur”) connects the upper portion of the generally vertical femoral shaft with a generally horizontal femoral neck having a somewhat smaller cross section, which in turn terminates in an enlarged spherical femoral head which is adapted for rotation in a respective spherical socket (in latin “acetabulum”) on each side of the human pelvis. The intertrochanteric region is defined by two enlarged prominences—a greater trochanter having a relatively flat, broad surface on the outside of the femur and a lesser trochanter having a relatively short conical surface on the inside of the femur—to which are attached various muscles and ligaments, including those which connect the thigh to the pelvis.
The upper portion of the femur and in particular its intertrochanteric and adjacent neck regions are critical paths for weight bearing through the skeletal system and are therefore subject to comparatively high levels of dynamic stress, nail pathological strain, physiological strain, and trauma. In particular, this region is prone to fractures due to high velocity trauma in the young and trivial trauma in the elderly. The fractures in this area are called intertrochanteric fractures (in common parlance, “hip fractures”) and are classified as per the pattern of the fracture geometry. After such a fracture, the resultant bone tissue fragments are notorious for re-uniting in varying, and sometimes problematic angles relative to each other and to the intramedullary portion of the femur. Therefore, a hip fracture typically requires early surgical reduction and fixation followed by prompt commencement of mobilization and weight bearing in order to facilitate enhanced recovery.
Particularly in the elderly, osteoporosis (reduced density and impaired structural integrity) of the bone tissue in this area further increases the risk of complex fractures and problematic functional recovery. The World Health Organization Fracture Prediction Tool, or WHO FRAX for short, is a recognized and accepted tool for predicting susceptibility to hip fractures, and can be downloaded on the internet. Accordingly, recognized experts such as The American Academy of Orthopedic Surgeons (AAOS) have officially encouraged orthopedists to become involved in “bone fragility” screening to create clinics that use statistical screening and bone density studies to identify patients that are at significant risk for hip fracture and that would benefit from prophylactic treatment with prolia or boniva or other appropriate medications to prevent further bone loss.
Repair and reinforcement of complex fractures of the femoral shaft using elongated intramedullary nails has been a standard surgical procedure since World War I, and threaded nails (screws) have been used both to facilitate realignment of the separated intertrochanteric bone fragments and to apply tension to hold them in position. More recently, combinations of intramedullary nails and intertrochanteric screws have been commercially available for repairing existing hip fractures in the intertrochanteric and adjacent femoral neck regions by realigning the bone fragments and applying tension to promote healing. Although in theory such known hip fracture repair devices could be used prophylactically to provide protection from future fractures in an intact femur, the known devices and surgical procedures are relatively complex, invasive, and time consuming, and any such prophylactic use is neither medically advisable nor cost effective.